sorel



Nov. 27 1923. 1,475,520

M. E. D. SQREL PISTON FOR INTERNAL COMBUSTION ENGINES Filed Dec. 27.1920 2 Shuts-Shoot l //v v E N T o R Maurice Etienne Ds tr SON/L.

New. 27 1923, 1,475,520

M. E. D. SOREL PISTON FOR INTERNAL COMBUSTION ENGINES Filed Dec. 27.1920 2 Sheets-Shut 2- II/Ill INVENTOR Mwurzlcc Etienne De'sir 5on1.

Patented Nov. 27, 1923.

PATENT OFFICE.

MAURICE ETIENNE DESIRE SOREL, or PARIS, FRANCE.

PISTON FOB INTERNAL-COMBUSTION ENGINES.

Application filed December 27, 1921.

To (ZZZ whom it may concern:

Be it known that I, MAURICE ETIENNE Liisrnri SoREL, a citizen of France,and resident of 2% Rue de Bondy, Paris, France, founder, have inventedImprovements in Pistons for Internal-Combustion Engines, of which thefollowing is a full, clear, and exact description.

Aluminum pistons provided with contin- 1O uous rings made of a metal,such as iron, having a coefficient of expansion lower than that ofaluminum, have already been proposed, these rings being made smooth attheir upper and lower faces so as not to adhere to the piston and sothat they are radially movable. Owing to this radial movement of therings, shocks necessarily take place, either of the piston against thewall of the cylinder, or of the inner face of the rings against thebottom of the grooves of the piston, and such shocks cause noise.

The present invention relates to an improvement in pistons of this type,and has for its main object to do away with all noise.

In the improved device forming the subject-matter of this invention, therings are firmly held in the body of the piston so as to be virtuallyintegral with the latter so that they cannot be subjected to any radialdisplacement.

In accordance with the present invention, internal combustion enginepistons are made of aluminum or other metal having a coefficient ofexpansion substantially greater than that of the engine cylinder, andthe invention consists in the application to such pistons of one or morevirtually integral hoops or rings characterized by the double followingcondition:

(a) The metal constituting this hoop or hoops has a coell'icicnt ofexpansion equal or sensibly equal to that of the metal constituting thecylinder of the engine;

(6) The external diameter of this hoop or hoops is very slightly greaterthan that of the aluminum piston when it is cold, and is determined insuch a manner that the play of this hoop or hoops in the cylinder of theengine is equal to that given to cast iron pistons.

In these conditions, the aluminum piston, guided by the said hoop orhoops, acts as a cast iron piston, whilst maintaining the advantages ofaluminum pistons.

Preferably, the respective diameters of the Serial No. 433,339.

hoop or hoops and of the piston are determined in such a manner that,when the engine rotates at slow speed, that is to say when the piston iscold or at a low temperature, the hoops alone bear against the wall ofthe engine cylinder and that, on the contrary, when the engine rotatesat its working speed and the temperature of the piston is high, thealuminum piston, owing to its expansion greater than that of the hoops,rubs against the wall of the cylinder.

The accompanying drawing shows, by way of example, two forms ofexecution of the invention.

Fig. 1 illust'ates, in vertical section, an aluminum piston provided atits lower part with a cast iron hoop.

Fig. 2 is a horizontal section made according to line AA of Fig. 1.

Fig. 3 shows, also in vertical section, another form of execution inwhich the piston is provided with two cast iron hoops respectivelyarranged above and below the bearings adapted to receive the axis of thepiston by means of which the latter is hinged to the connecting rod.

Fig. i is a horizontal section made according to line B--B of Fig. 3.

In the form of execution ilustratecl in Figs. 1 and 2, at the base ofthe aluminum piston a is fixed a hoop Z) made of cast-iron, iron, steelor other metal having a coefficient of expansion equal or sensibly equalto that of the cylinder of the engine; this hoop is, prefer ably,embedded in the lower part of the pis ton and is secured in position inthe following manner:

At the lower part of the mould in which the aluminum piston is to becast, the hoop b is arranged (before casting the metal) in a grooveformed for that purpose in the mould. Upon casting of the aluminum, thelatter surrounds this hoop on its inner face and its two upper and lowerfaces.

The machining of the aluminum piston thus provided with its hoop b iseffected in the ordinary manner, with sufficient play for avoiding anyseizing of this piston when the engine rotates at high speed.

On the contrary, the hoop b is turned exactly according to the samedimensions and with the same play as if it were a part of a piston madeentirely of cast-iron, that is to say with a diameter very slightlygreater than that of the aluminum piston.

The piston a, thus guided by its hoop 6, acts therefore as a cast-ironpiston, whilst having the advantages of an aluminum piston.

For avoiding any risk of breaking of the hoop 7) under the effect of theexpansion of the piston, recesses 0 can be provided in the inner boss (0of the piston.

The hoop Z), instead of being embedded in the metal of the piston, couldbe mounted, after machining of the latter, by means or a press.

The piston u. might also be screw threaded and the hoop Z) provided withfemale thread, so that the said hoop may be mounted by screwing.

It is to be understood that the hoop i) can be secured on the piston byany mechanical means and mounted at any suitable point of the latter.

The hoop 5 could have a suflicient height for guiding the piston on arather great length; if necessary the pivoting axis of the piston mightpass through this hoop.

In the form of execution illustrated in Figs. 3 and i, the aluminumpiston a is provided with two hoops 6 made of cast-iron, iron, steel orother metal having a coeflicient of expansion equal or sensibly equal tothat of the cylinder of the engine; these two hoops are respectivelymounted above and below bearings 0 adapted to receive the pivoting axisof the piston, between these hearings and the rings mounted at both endsof the piston.

These hoops could also be interposed between the said rings or arrangedbeyond the latter.

The piston is moulded or cast as an ordinary aluminum piston. either insand or, preferably, in a metallic mould which permits of obtaininggreater precision in the placing in position of the hoops.

The hoops are previously placed in position in the mould before castingthe aluminum.

These hoops have an external diameter sensibly greater than thatpresented by the piston asit comes out from the foundry, in order tooffer a bearing i'ierlnitting to place them easily in the mould. \Vhentaken oil? the mould, the hoops project therefore on the outer surface(it the piston and are in contact with the metal of the latter on threefaces: on their inner face and on their two upper and lower faces. Owingto shrinkage of the aluminum, upon cooling of the piston after removalfrom the mould, the hoops Z) are tightly embraced in the piston.

The piston is then machined.

The aluminum piston proper is turned to the diameter which is generallygiven to aluminum pistons, that is to say with a play which will beabout 18/10 of the play normally given to a cast-iron piston. The

hoops, on the contrary, are turned to the diameter which generally givento castiron pistons.

Owing to the difference of the diameters given to the hoops and to thepiston and to the difference of the coeliicients or expansion of themetal constituting these hoops and ot the aluminum of the piston, therubbing surfaces of the latter will he sometimes the hoop when, theengine rota-ting at small speed, the tem nerature of the. piston will below, sometimes the aluminum body of the piston when, the engine rotatingat its working speed, the temperature oi the engine will have raised.The original diameters of the hoops and of the aluminum body can bedetermined so that, in the latter case, the hoops are slightly ojll' setrelatively to the outer surface of the expanded piston.

In these conditions, the hoops rub on the cylinder wall only when theengine rotates at small speed and the wear of the same will then be veryslight.

It is also to be noted that, in the case of motor car engines, to whichthe piston tormi-ng the subject-matter of this invention is moreparticularly applicable, the time when the hoops rub against thecylinder corresponds to slow speed running or to running light whenthrowing out of gear, that is to say at the time where the reactionstresses of the piston against the cylinder are very small.

By means of this device, the wear of the hoops is considerably reduced.

The present improvement, more particularly applicable to the pistons ofmotor car engines, may, however, also be applied to the pistons of anyinternal combustion engines.

It is to be understood. that the number of hoops may be varied accordingto the applications.

Claims:

1. A piston for internal combustion engines, made of a metal thecoefficient of can pansion of which is substantially greater than thatof the metal of the cylinder, hav ing virtually integral therewithnon-sectioned continuous rings made 01" a metal having a coefficient 0,expansion substantially equal to that of the metal oi the cylinder oithe engine. having when cold an outer diameter slightly greater thanthat of the piston body, the outer diameters of these rings and of thepiston'body being such that, when cold and at low temperatures, therings alone rub against the inner wall of thecylinder whilst at hightemperatures, the piston body, owing to its co efficient of expansionbeing greater than that of the metal of the rings, also rubs against thewall of the cylinder.

2. an aluminum piston for internal combastion engines, having anon-sectioned eontinuous ring made of a metal having virtually integraltherewith a coeflicient of expansion approximately equal to the metal ofthe cylinder of the engine, having when cold an outer diameter slightlygreater than that of the body of the aluminum piston, the outerdiameters of this ring and of the piston body being such that when atlow temperatures the ring alone rubs against the inner wall of thecylinder Whilst on the contrary, at high temperatures, the aluminum bodyof the piston and the ring both rub against the Wall of the cylinder,owing to the coeliicient of expansion of aluminum 1 being greater thanthat of the metal constituting the ring- 3. An aluminum piston forinternal com bustion engines, having, arranged on opposite sides of thepivotal axis of the piston, and virtually integral therewithnon-sectioned continuous rings made of a metal having a coeflieient ofexpansion approximately equal to that of the metal of the cylinder ofthe engine and having When cold an outer diameter slightly greater thanthat of the body of the aluminum piston, the outer diameters of theserings and of the piston body being such that at low temperatures therings alone rub against the inner Wall of the cylinder, whilst on thecontrary at high temperatures, both the aluminum body of the piston andthe rings rub against the Wall of the cylinder, owing to the coeflicientof expansion of aluminum being greater than that of the metalconstituting the rings.

The foregoing specification of my improvements in aluminum pistons forinternal combustion engines, signed by me this 7th day of December,1920.

MAURICE ETIENNE DESIRE SOR-EL.

